ON THE SUPERSTABILITY OF THE GENERALIZED SINE FUNCTIONAL EQUATIONS

Inthispaper,westudythesuperstabilityproblembounded by two-variables of Th. M. Rassias type for the generalized sine func- tional equations g(x + y)f(x − y) = f(x)^2 − f(y)^2 f(x + y)g(x − y) = f(x)^2 − f(y)^2 g(x + y)g(x − y) = f(x)^2 − f(y)^2, which does not use his iteration method.